This proposal seeks funding for the purchase of an LTQ Velos Pro mass spectrometer from ThermoFisher, with ETD option and nanoLC. The combination of fast cycle times, high sensitivity and multiple ion fragmentation modes provided by this instrument is not available to the major user group for this proposal, yet would allow fundamental enhancements in quantitative proteome- and quantitative phosphoproteome-based mass spectrometry experiments in support of a number of NIH funded research programs at UCI. Specific projects that will be enhanced include investigation of the molecular mechanisms underlying the modulation of cell signaling upon infection by vaccinia virus (Dr. Gershon); global cellular responses to polio and rhinovirus (Dr. Semler) and Chlamydia infection (Dr. DeLa Maza), understanding the salivary gland and midgut responses of mosquito vectors to infectious diseases (Dr. James), early detection of prostate cancer markers in the urinary proteome (Dr. Mercola), global changes in phosphosite occupancy as a result of Pim-1 kinase over-expression and specific inhibition (Dr. Lilly), finding growth factors involved in blood vessel branching durig embryogenesis and their homeostasis (Dr. Hughes), plasticity of modifications incurred during the assembly of human mRNA splicing complexes (Dr. Hertel), understanding responses to protein aging in the brain, and molecular dynamics of the key regulatory enzyme nitric oxide synthase (Dr. Poulos). The P.I. of this proposal, with 12 years experience in protein mass spectrometry, will administer the instrument in a shared area with the blessing of the aforementioned collaborators under the oversight of a supervisory committee with external members including Dr. Joe Loo (UCLA) and Dr. Julian Whitelegge (UCLA), and internal committee members representing both basic and clinical programs. 21 NIH-supported research programs related to human health spanning six departments in two schools of UCI are expected to benefit significantly from the capabilities of the proposed instrument. The requested instrument would represent a significant advance in interdisciplinary biomedical research capabilities within the UCI Schools of Medicine and Biological Sciences.